Communication system with cordless system units connected to a communication network

ABSTRACT

A communication system has cordless system units (1, 2, 3, 4) connected to a communication network (7). The cordless system units respectively has at least one cordless base station (11-13, 21-23, 31, 32, 41). The identification of a respective cordless terminal equipment (8) is stored in a cordless system unit (1, 2, 3, 4) allocated thereto as a home system unit. The possibility or, respectively, allowability of a connection setup from the respective cordless system unit (1, 2, 3, 4) to a cordless terminal equipment (8) can be checked by a check apparatus (15, 25, 35, 45) respectively allocated to the cordless system units (1, 2, 3, 4). The cordless system units (1, 2, 3, 4) are connected to a network (6, 61) offering a connectionless service in order to exchange information with one another dependent on check results of the check apparatus (15, 25, 35, 45).

BACKGROUND OF THE INVENTION

The invention is directed to a communication system.

Such a communication system is disclosed by European reference EP-0 433256-A2. In this communication system, a cordless terminal equipment isnormally authorized for connections via a specific cordless system unit.Cordless system units serve for connecting cordless terminal equipmentto a communication network. Such a communication network can be aprivate branch exchange that is in turn usually connected to a regionalor global network. In some instances, a cordless system unit itself canfulfill jobs of a private branch exchange.

A cordless system unit controls the recognition of the presence of anoperational cordless terminal equipment in the transmission andreception area of one of its base stations and the routing of aconnection setup to this terminal equipment via this base station(roaming according to ETS 300 175-3). To this end, it contains a checkmeans for checking whether a connection setup from it to a cordlessterminal equipment is possible. Such a connection setup is possible whenan information exchange between at least one of the base stations of thecordless system unit and the cordless terminal equipment can betechnically implemented via the cordless transmission/reception link.Given an information exchange by analog signal transmission, onecriterion therefor can be the achieving of an adequately high receptionsignal level and, given an information exchange by digital signaltransmission, can be the achieving of an adequately low bit error rate.Whether a connection setup is possible is essentially dependent onwhether the cordless terminal equipment is operationally located in thetransmission and reception area of a base station of the cordless systemunit.

Given an existing connection between the cordless terminal equipment anda communication network connected to the cordless system unit, thecordless system unit--in conjunction with its base stations--controlsthe connection setup via the one base station and the new connectionsetup via the other base station given an area change of the cordlessterminal equipment from one base station to a neighboring base station(handover according to ETS 300 175-3).

In order to monitor the access authorization of a cordless terminalequipment to the communication system and in order to monitor whether acordless terminal equipment is authorized to initiate a connection setupvia the cordless system unit, the check means checks the permissibilityof such a connection setup. A cordless terminal equipment is usuallyauthorized to initiate a connection setup via a cordless system unitwhen this is administratively allocated to it as home system unit. Whena cordless system unit is allocated to a cordless terminal equipment ashome system unit, then its identification is stored in it.

Base stations serve first and foremost for the bidirectional conversionof cordlessly transmitted signals and signals transmitted wire-bound.For example, a cordless signal transmission can be undertaken byinfrared signal or by radio. For example, the DECT method described inthe ETS 300 175 can be cited as a radio transmission method. A cordlesssystem unit can have one or more base stations.

When, in a communication known from European reference EP-0 433 256-A2,a cordless terminal equipment is to be operated in the transmission andreception area of a cordless system unit that is not allocated to it ashome system unit, then it must be reported at the administration of thissystem unit. To this end, every cordless system unit keeps a definedplurality of telephone numbers on hand that cannot be assigned topermanently allocated terminal equipment.

In such a communication system, consequently, a cordless terminalequipment can only be operated in the transmission and reception area ofits home system unit or in the transmission and reception area of acordless system unit at which it is temporarily administrativelyreported. The initiation of a connection setup by this cordless terminalequipment is deemed allowable by the check means of a cordless systemunit only in these cases. The number of terminal equipment that can besigned on per administration for a cordless system unit in addition tothe permanently allocated cordless terminal equipment is limited by thenumber of telephone numbers offered for these purposes. Since theindividual cordless system units must offer additional free telephonenumbers for the temporary logon of cordless terminal equipment, theinstalled resources of the communication system cannot be optimallyexploited.

SUMMARY OF THE INVENTION

An object of the invention is to offer a communication system thatenables a simple access of cordless terminal equipment to thecommunication system in the transmission and reception area of arbitrarycordless system units.

The inventive communication system contains cordless system unitsconnected to a communication network, each of the cordless system unitshaving at least one cordless base station. The identification of arespective cordless terminal equipment is stored in a cordless systemunits allocated thereto as a home system unit. The possibility or,respectively, allowability of a connection setup from the respectivecordless system unit to a cordless terminal equipment can be checked bya check means respectively allocated to the cordless system units. Thecordless system units are connected to a network offering aconnectionless service in order to exchange information with one anotherdependent on check results of the check means.

Due to the communication of the information between the cordless systemunits via a network offering a connectionless service, apoint-to-multipoint inquiry can be communicated to all cordless systemunits belonging to the communication system without an involved layer-3signaling.

When, for example, the check by the check means of the home system unitdetermines that a called cordless terminal equipment is not located inits transmission and reception area, then the home system unit caninquire in a simple way at all connected cordless system units via thenetwork offering a connectionless service whether a connection setup tothe cordless terminal equipment is possible from the check means of anyother cordless system unit of the communication system. When thecordless terminal equipment is located in the transmission/receptionarea of a base station of another cordless system unit, this informs thecommunication system, potentially via the network offering theconnectionless service, and informs the home system unit, and thecommunication system can connect the incoming call to the calledcordless terminal equipment. Such a connection setup can thereby beconducted via the home system unit and an additional connection from thehome system unit to the cordless system unit in whose area the terminalequipment is located. In most cases--particularly when the home systemunit and the cordless system unit in whose area the terminal equipmentis located are connected to the same switching network of, for example,a private branch exchange--, however, it is advantageous to connect theincoming call directly via the cordless system unit in whose area theterminal equipment is located. The arising call data can then becommunicated between this system unit and the home system unit via thenetwork offering the connectionless service.

When, for example, a cordless terminal equipment that is located in thetransmission/reception area of a base station of a cordless system unitthat is not allocated to it as home system unit wants access to thecommunication system in order to initiate a connection setup, then theallowability check by the check means of these cordless system unitshows that the identification of this cordless terminal equipment is notstored at it. In this case, the cordless system unit can inquire in asimple at all connected cordless system units via the network offering aconnectionless service whether the cordless terminal equipment hasauthorization to access the communication system, i.e. whether itsidentification is stored in any cordless system units of thecommunication system. When a cordless system unit of the communicationsystem is home system unit of the cordless terminal equipment, this cancommunicate corresponding information to the inquiring cordless systemunit via the network offering a connectionless service. This cansubsequently enable an access of the cordless terminal equipment to thecommunication system. The arising call data can then be communicatedbetween this system unit and the home system unit via the networkoffering the connectionless service.

Connectionless service here means connectionless with respect to layer 2and, potentially, layer 3 according to the OSI reference model (ISO 7498of 1993).

For example, a datagram-oriented local network referred to as LAN (fromthe English local area network) can be provided as a network offeringconnectionless service. The Ethernet defined in the standardizationpublications IEEE 802.3 and IEEE 802.5 can be cited as an example of adatagram-oriented local network. When the individual cordless systemunits of the communication system are arranged at a great spacing fromone another in a regional or global company network, the networkoffering a connectionless service can be composed of two or more localnetworks that form a network union via dedicated lines or via a regionalor global network. Such networks offering a connectionless service aredescribed, for example, in the book SMDS Wide-Area Data Networking withSwitched Multi-megabit Data Service by R. W. Klessig and K. Tesink,Prentice Hall, 1995, particularly pages 11 through 14.

Preferably, the overall network offering a connectionless servicecontains a single controller for the monitoring of the accessauthorization of connected cordless system units to this network and forrejecting unauthorized access attempts. This controller can be realized,for example, by a central computer that monitors the coupling of remotecordless system units or of remote local networks of the networkoffering a connectionless service to a central network and can thusreject an unauthorized data exchange.

The receiving and sending of information by a party not authorized to doso that is authorized to access the network is very easily possible indatagram-oriented networks. For security reasons, particularly toprevent an unauthorized access to the communication system, it istherefore recommendable to provide a separate datagram-oriented networkthat serves exclusively for the information exchange between cordlesssystem units. When such a separate datagram-oriented network is composedof a plurality of local networks arranged at a great distance from oneanother, then remote local networks or individual, remote cordlesssystem units as well are connected to a central local network,preferably via a permanently set up point-to-point connection such as,for example, a dedicated line, in order to prevent an unauthorizedaccess via a datagram-oriented long-distance network.

In order to connect individual, remote cordless system units to thecommunication system, the connection between the separatedatagram-oriented network and these remote cordless system units that isrequired in the physical layer of the network offering a connectionlessservice can also be realized as a dialed connection as needed. In thiscase, the controllers of the cordless system units and/or the centralcontroller of the datagram-oriented network must initiate the requiredconnection setup.

As an exemplary embodiment of the invention, the single FIGURE shows acommunication system with cordless system units 1, 2, 3 and 4 connectedto a communication network 7. Each of the cordless system units 1, 2, 3and 4 has a controller 10, 20, 30 and 40 as well as base stations 11,12, 13, 21, 22, 23, 31, 32 and 41. In the illustrated exemplaryembodiment, the cordless system units 1 and 2 each have respectivelythree base stations 11, 12, 13 and 21, 22, 23, the cordless system unit3 has two base stations 31 and 32, and the cordless system unit 4 hasone base station 41. The controller 10, 20, 30, 40 of each cordlesssystem unit 1, 2, 3, 4 contains a check means 15, 25, 35, 45 as well asa memory means 14, 24, 34, 44 unto which the identification of thecordless terminal equipment 8 to which the cordless system unit 1, 2, 3,4 is allocated as home system unit is respectively programmed. A singlecordless terminal equipment 8 is shown in the exemplary embodiment.

The cordless system units 1, 2, 3 and 4 shown in the single FIGURE arerespectively connected via an interface arrangement 16, 26, 36, 46 to anetwork 6 offering a connectionless service. In the exemplary embodimentof the FIGURE, this network 6 offering a connectionless service iscontrolled by a central control means 61, for example a microcomputer.

In the illustrated exemplary embodiment, the cordless system units 1 and2 are respectively connected to the switching network 71 of a privatebranch exchange, and this switching network 71 is connected to a globalcommunication network 72. The cordless system units 3 and 4 arerespectively directly connected to the global communication network 72.

The functioning of a communication system according to the exemplaryembodiment of the single FIGURE is described below given the assumptionthat the cordless system unit 1 is allocated to the cordless terminalequipment 8 as home system unit, and that the cordless terminalequipment 8 is located in the transmission and reception area of one ofthe base stations 31 and 32 of the cordless system unit 3 and isoperational.

When an attempt is made in the described case proceeding from thecordless terminal equipment 8 to initiate a connection setup via thecordless system unit 3 to the communication network 7, then the checkmeans 35 checks on the basis of the memory entries in the memory 34whether it is the home system unit of the cordless terminal equipment 8.Since this is not the case, an inquiry as to whether the connectionsetup requested by the cordless terminal equipment 8 is allowable iscommunicated to the other system units 1, 2 and 4 of the communicationsystem via the interface arrangement 36 and the network 6 offering aconnectionless service. This inquiry proceeding over the interfacearrangement 16 to the controller 10 of the cordless system unit 1 leadsto a check by the check means 15 of this system unit 1. The accessattempt by the cordless terminal equipment 8 is found to be allowable inthe system unit 1. The controller 10 of the cordless system unit 1subsequently communicates the information that the access attempt isallowable to the cordless system unit 3 via the interface arrangement16, the network 6 offering a connectionless service and via theinterface arrangement 36 and--when necessary--also communicates furtherinformation required for a connection setup. As a result thereof, thesystem unit 3 treats the cordless terminal equipment 8 as though it wereallocated to it as home system unit.

The control unit 61 monitors all said accesses onto the network 6offering a connectionless service as to their allowability.

When, in the aforementioned case, the inquiry for a connection setup tothe cordless terminal equipment 8 arrives at the cordless system unit 1via the global network 72 and the switching network 71 of the privatebranch exchange, then the check means 15 of the cordless system unit 1checks whether a connection setup to the cordless terminal equipment 8is possible. In the described case, such a connection setup via thecordless system unit 1 is not possible. In response thereto, thecontroller 10 of the cordless system unit 1 communicates an inquiry tothe cordless system units 2, 3 and 4 via the interface arrangement 16and the network 6 offering a connectionless service as to whether aconnection setup to the cordless terminal equipment 8 is possible viathese cordless system units 2, 3 and 4. This inquiry proceeds via theinterface arrangement 36 to the controller 30 of the cordless systemunit 3, whereupon the check means 35 thereof checks whether therequested connection setup is possible. The positive check result iscommunicated via the interface arrangement 36, the network 6 and theinterface arrangement 16 to the controller 10 of the cordless systemunit 1. In response thereto, the controller 10 of the cordless systemunit 1 initiates a connection setup to the cordless terminal equipment 8via the cordless system unit 1.

BRIEF DESCRIPTION OF THE DRAWING

The features of the present invention which are believed to be novel,are set forth with particularity in the appended claims. The invention,together with further objects and advantages, may best be understood byreference to the following description taken in conjunction with theaccompanying drawing, in which:

The single FIGURE depicts an exemplary embodiment of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention is not limited to the particular details of the apparatusdepicted and other modifications and applications are contemplated.Certain other changes may be made in the above described apparatuswithout departing from the true spirit and scope of the invention hereininvolved. It is intended, therefore, that the subject matter in theabove depiction shall be interpreted as illustrative and not in alimiting sense.

What is claimed is:
 1. A communication system comprising:cordless systemunits connected to a communication network each of said cordless systemunits respectively comprising at least one cordless base station and acheck apparatus; a respective cordless terminal equipment having anidentity that is stored in one of said cordless system units allocatedto said cordless terminal equipment as a home system unit, and wherebyan allowance of a connection setup from the respective cordless systemunit to a cordless terminal equipment being checked by a check apparatusrespectively allocated to the cordless system units; and a networkoffering a connectionless service for bidirectionally exchanginginformation between said cordless system units via said network, saidcordless system units being connected to said network, and saidinformation being exchanged dependent on check results of one of saidcheck apparatuses.
 2. The communication system according to claim 1,wherein the network offering a connectionless service is adatagram-oriented network.
 3. The communication system according toclaim 2, wherein the datagram-oriented network is exclusively providedfor the information exchange between cordless system units.
 4. Thecommunication system according to claim 2, wherein the datagram-orientednetwork is a local network.
 5. The communication system according toclaim 2, wherein the datagram-oriented network is composed of at leasttwo coupled local networks.
 6. The communication system according toclaim 2, wherein the datagram-oriented network has a single controllerfor monitoring access authorization of connected cordless system unitsonto said network and for rejecting unauthorized access attempts.
 7. Thecommunication system according to claim 6, wherein the datagram-orientednetwork has a central local network to which at least one of remotecordless system units and remote local networks of the datagram-orientednetwork are respectively coupled via a permanent point-to-pointconnection.
 8. The communication system according to claim 3, whereinthe datagram-oriented network is a local network.
 9. The communicationsystem according to claim 3, wherein the datagram-oriented network iscomposed of at least two coupled local networks.
 10. The communicationsystem according to claim 3, wherein the datagram-oriented network has asingle controller for monitoring access authorization of connectedcordless system units onto said network and for rejecting unauthorizedaccess attempts.
 11. The communication system according to claim 10,wherein the datagram-oriented network has a central local network towhich at least one of remote cordless system units and remote localnetworks of the data-oriented network are respectively coupled via apermanent point-to-point connection.